Perforated metal sheets are more rigid and can be made stronger than woven wire cloths and so they find particular applications in strainers, coarse filters and screens. Perforated metal strainers have a predictable and consistent performance because the size of the screen openings is controlled in the manufacturing process. In their simplest form they can […]
The crimping of the individual wires in a mesh goes a long way towards ensuring the stability of the mesh, and therefore the constancy of the apertures of the mesh, if the mesh is subject to movement or vibration in use. Where absolute stability is required, this can be achieved by sintering the mesh, so […]
The weave of any mesh is usually one of six basic types, but there are also some minor variations. Square mesh (Figure 2.9) has each weft wire passing alternately over and under each warp wire. The opening can be square or rectangular (much less commonly) and so this weave is more correctly referred to as […]
The weaving of wire is no different, in principle, from the weaving of any other yarn: warp wires are set up along the loom and weft wires across it. The product is a roll of woven mesh, which then is processed in a variety of ways, to produce the filter medium (or for many other […]
Media made from metals have already been mentioned, in Section 2C, in the form of sheets and tubes made from metal fibres and powders, usually sintered together to retain their structure. By far the greatest amount of filter media made from metal, however, is in the form either of woven wire or perforated sheets, which […]
As already mentioned, a major feature of the inorganic materials included here is their ability to operate at high temperatures. The importance of this particular set of applications is continually growing. Classed under this heading are media made from metal powder and fibres, ceramic powder and mineral wools, glass powder and carbon fibres (used for […]
There is an important group of media materials that are not fabrics in the normally accepted sense of the word, because they are mostly not flexible, but they are made in similar ways, and serve a similar purpose, so they are included here. These are the sheets and tubes made from bonded components: fibres and […]
Just as needlefelts took market shares from some woven fabrics as filter media, so now are the newer meltspun synthetics expanding quickly into most filtration applications. These are the class of media that start with a filament of molten thermopolymer being extruded from a fine nozzle. As it leaves the nozzle the filament is quenched […]
For some, undemanding, applications, a simple felt can provide suitable filtration performance, without any form of strengthening. However, their low tensile strengths, and the ease with which fibres can become detached, make simple felts unattractive for most filtration purposes, and some mechanical (or chemical) strengthening is required. Needle punching is the most common mechanical strengthening […]
It is a common feature of solid/gas filtration, and, to a lesser extent, solid/liquid filtration, that the particles in suspension may carry an electrostatic charge, and therefore that a filter medium carrying the opposite charge will be more effective in their removal. Many different media can be given a charge for this purpose, but one […]
